1) Host Pathogenesis. Chronic lung infections associated with nontuberculous mycobacteria (NTM) often occur in the setting of known structural lung disease such as COPD or bronchiectasis associated with cystic fibrosis or primary ciliary dyskinesia. Our observational cohort study serves as the backbone for pathogenesis research focused on patients with idiopathic nodular bronchiectasis associated with NTM infection occurring predominantly in older women. We recently described the importance of careful phenotyping, endotyping and assessment of associated genetic risk alleles in characterizing bronchiectasis and associated infections such as NTM (Lancet 2018). The success of therapeutic interventional trials, such as those leading to FDA approval of amikacin liposome inhalation suspension as the first approved drug for management of pulmonary NTM disease, is dependent on careful selection of target populations and reduction of underlying disease heterogeneity to accurately detect drug efficacy (Am J Respir Crit Care Med 2018). With success of these trials, interest is building in better characterizing pulmonary nontuberculous mycobacterial infections and we participated in defining a roadmap for advancing translational science in this field (Am J Respir Crit Care Med 2019). (2) Epidemiology. In 2008 our lab along with extramural academic partners developed a US Bronchiectasis Research Registry that has been administered by the COPD Foundation. This Registry has enrolled over 3000 patients in the US and is being used as a source of participants in clinical trials and for epidemiologic research. Continued analysis of Registry data focused on describing differences in patients with bronchiectasis associated with alpha-1 antitrypsin deficiency, common variable immunodeficiency and primary ciliary dyskinesia (Chronic Obstr Pulm Dis 2019). To assess the burden of NTM pulmonary disease, we examined claims from a large US managed care database to determine all-cause mortality in patients with NTM lung disease. Patients with NTM lung disease had substantially higher co-morbidities of asthma (23.3% versus 3.5%), bronchiectasis (36.5% versus 0.1%), COPD (52.0% versus 5.9%), arrhythmia (22.6% versus 6.5%), coronary artery disease (18.5% versus 6.6%), heart failure (11.9% versus 4.1%), and cancer (18.5% versus 5.0%) and a doubling risk of all-cause mortality (adjusted hazard ratio HR=2.06; CI: 1.52-2.79; P<0.001) compared to a control group (Respir Med 2018). Considerable variability of treatment for pulmonary NTM has been previously noted. We examined treatment of pulmonary M. avium complex (MAC) utilizing a national hospital database and noted of 1326 MAC patients, 645 (49%) received treatment. Only 10% received guidelines-based treatment and 18% received treatment that has been associated with development of macrolide resistance. (3) Microbial pathogenesis and therapeutics assessment. Work over the past year has focused on utilizing a laboratory zebrafish infection model to assess relative virulence of serial clinical isolates of M. abscessus obtained from patients over the course of their disease. An amoeba model was used to assess the effectiveness of synthetic antimicrobial peptides against clinical strains of M. abscessus. In collaboration with the NIH Clinical Center Mycobacteriology Lab we assessed the performance of a new selective media to improve detection of NTM in respiratory specimens from our patients. Recovery of NTM was significantly higher with the RGM30 media than that of either the MGIT system (76.7% versus 59.4%; P=0.01) or Middlebrook 7H11 agar (76.7% versus 47.4%; P=0.0001) alone (J Clin Microbiol 2019). Amikacin is a highly effective drug against many species of NTM but it has a limited therapeutic window and mutations associated with constitutive resistance have been described in association with reduced clinical benefit. We assessed the potential for amikacin resistance in a selected cohort of patients with prolonged exposure (median 2.3, range 0.6-8.6 years) to amikacin treatment. Only 1 of 16 patients with antimicrobial susceptibility testing by broth microdilution and genetic markers of resistance of 1st and last isolates was noted to have a resistant final isolate (MIC >64gmL-1), accompanied by an AG mutation at position 1408 of the 16S ribosomal RNA (ERJ Open Research 2019). Work has begun on development of an altered airway clearance mouse model of chronic M. abscessus infection to further aid with virulence and therapeutic intervention development studies.